DESCRIPTION: Acanthamoeba keratitis has been considered a relatively rare and severe form of corneal infection which causes debilitating visual loss. It has most frequently been associated with the use of contact lenses. The diagnosis is confirmed with a simple epithelial biopsy and histologic examination by an ophthalmic pathologist. In the last three years, we have examined 400 patients with keratitis and have identified 106 patients with presumed Acanthamoeba in the cornea, each subsequently confirmed with an epithelial biopsy. In only one case have we been successful in culturing the organism. It is the PI general hypothesis that Acanthamoeba keratitis represents an underdiagnosed opportunistic infection of the human cornea which can present a significant health hazard. It is much more common than previously thought. The diagnosis and management of this disease will be greatly improved with more precise and rapid diagnostic tools including confocal microscopy and polymerase chain reaction (PCR). We propose in this research to: 1) Determine the prevalence of subclinical or asymptomatic Acanthamoeba infection in the normal population by examining, with confocal microscopy, a series of normal patients and patients undergoing epithelial removal prior to PRK for myopia. Examine Eye Bank eyes with confocal microscopy, histology, and PCR for the presence of amoeba. 2) Determine the prevalence of clinical, subclinical, or asymptomatic corneal acanthamoeba infections in patients with various forms of keratopathy including presumed bacterial keratitis, diabetic epitheliopathy, basement membrane dystrophy, herpes simplex keratitis and herpes zoster keratitis and confirm the diagnosis with histology, culture and PCR. 3) Determine the prevalence of clinical or subclinical acanthamoeba infection in patients particularly prone to acute infection including patients wearing contact lenses who have normal epithelium or evidence of epithelial disease such as punctate keratitis or microcysts. Patients with clinical and confocal evidence of disease will have an epithelial biopsy for further diagnosis. 4) Characterize the organisms we have identified by developing a polymerase chain reaction (PCR) assay, enhance our culture techniques, and thereby characterize more precisely these organisms.